Welcome to GS! Very clean mods. The insulated board is a nice touch. My instinct is to paint it white on top with elastomeric paint to keep the cargo bed cool, but form a style POV, it's better as is. Your MPG calcs are spot-on.
Looks like you have done a lot so far. You know, to a lot of people, its not geting the 30-40-50MPG, its making the best of what they have.
Now, I have to ditto the idea on the synth fluid.[whatever brand] is it a 4wd?? If so I bet you gain a lot changing all the dif's, and cases over to synth. It has always worked well for me in the 4wd's I have had.
I added the lower grille / bumper seam block today. total cost $25.
Used aluminum channel for rigid backing, choroplast sign to give a backing to the flashing. Riveted the the flashing, choroplast, aluminum channel together. Put door trip all the way around, zip tied to convenient places inside.
I used gray/silver copper pipe insulation to stuff the large bumper seam. All in all, I think it looks pretty good for an afternoons work. Will see tomorrow if we get any improvements on the highway. Hoping for 24mpg hwy!
Just for my education, why can some cars/trucks get by with a complete grill block?
jeffreymccoy's F150 seems to be doing great with a full grill block, upper and lower. And I've read of others doing the same.
I don't mean to threadjack - just want to throw in my story for comparison.
I just finished redoing the front face on my car. '89 wagon, 2.3 liter engine, electric rad fan with LED on the dash to tell me when fan comes on. With a smallish intake below the bumper (about 2.5" x 24") and a slightly smaller one above, the fan comes on occasionally for interstate upgrades at about 75 deg. F or warmer outside temp. I had to enlarge the upper intake as the first "cut" caused the fan to come on far too often for my taste, the the engine temp also increased significantly. With the current openings it's OK but I wouldn't dare block it more, at least not for the current temps we're seeing.
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.